| Research Abstract |
In this study, we examined embryos, fetuses, and animals produced by microinsemination or nuclear transfer techniques using male germ cells to know their genetic and epigenetic changes, which play the most integral part of in the acquisition of the properties of male gametes. Expression analysis of imprinted genes in fetuses reconstructed from primordial germ cells at 11.5 dpc and 12.5 dpc demonstrated that erasure of the parental imprinting memory occurred at 11.5 dpc and has completed by 12.5 dpc. Analysis of fetuses derived from gonocytes at day 3.5 after birth indicated that the paternal imprinting has not yet established by this stage. The first wave round spermatids at 17 days of age participated in normal development into offspring, indicating that the paternal imprinting has completed before meiosis of the first wave of spermatogenesis. The chromosomes of primary spermatocytes, spermatogenic cells before meiosis, underwent normal meiotic divisions after introduced into MI oocytes, and subsequently supported full term development. Detailed gene expression analysis demonstrated that each imprinted gene has each own schedule of erasure and establishment of imprinting marks. The developmental ability of embryos reconstructed from primordial germ cells at 11.5 dpc suggested that the totipotency of the male germ cell genome is probably maintained until 11.5 dpc or a little earlier stage.
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